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The K8J project

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Arfang

Well-Known Member
Supporting Member
Joined
Aug 10, 2014
Messages
157
Location
Switzerland
Good day all,

I think it's time to finally present my project. It's a jet conversion of a Ka8B glider.

The goal from the get-go was to make a jet-powered conversion as inexpensive and simple as possible while being compliant with the french ultralight regulations. Also important was keeping the number of unknown factors down, focusing on having a flying airplane, improvements can always be added later.

The requirements for a single-seat ultralight were:

MTOM: 300 kg (661 lbs)
Vstall max: 65 kph (35 kts)
max engine power: 80hp

My personnal additional requirements were:

A minimum climb rate of 1.5 m/s (295 fpm) and enough fuel to gain approximately 3000 ft AGL in order to have enough altitude to switch to ''soaring mode'' before the engine runs out of fuel.

The choice of a glider airframe was motivated by the relatively high LD and low weight of this aircraft type, allowing good enough performance with only a small engine, reducing the cost. That and the fact that there are plenty of airworthy old gliders for sale at reasonable prices.

So I ran some numbers, compared several types of gliders and bought a Ka8B.

IMG-20180511-WA0001.jpg

Now to the ''build log'', note that not everything is mounted in place yet, I still need to do the engine installation and wiring, probably this week-end.

Added a nosewheel on the bottom of the skid, like on the Turbine 1-26. http://csanders2775.wixsite.com/turbineschweizer126
Chad Sanders was very helpful and provided more information about his nosewheel installation than I could ask for.

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Replaced the cockpit floor and seat, replaced the instrument panel with a custom one to accomodate the ''throttle'' and FADEC display.

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Designed an engine mount to install a 310N thrust engine on it. It's not retractable to keep the installation as simple as possible. The mount also holds the fuel pump and FADEC. The triangular structure on the left drawing is located on the left in the last image.

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3D printed fairings will slide over the mounts to cover the cables and fuel line.

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A 2.5 US gal fuel tank is located beneath the engine mount. I still consider making a custom one and I'd like to thank the HBA members who helped me but for now the goal is to keep it simple.

Removed several unnecessary elements like the second vertical speed indicator, second thermos bottle and tow hooks. The airframe ended up at the same weight as before the engine installation.

The airplane has now received a temporary permit to fly, if I'm not mistaken it will be the first 3-axis jet-powered ultralight under french UL regulations. It's also probably the cheapest private jet in the world.

First test flight will take place hopefully before the end of the month.
 
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